Nanoparticle technology has been developed for decades. Since nanoparticles have low toxicity and biocompatibility, nanoparticles are widely used in pharmaceutical formulations. The highly toxic drugs may be carried and encapsulated into the inside of nanoparticles to decrease their toxicity. However, nanoparticles have some main defects: low stability in blood, slow drug release, and large normal tissues accumulation. To overcome the defects, physical or chemical technology have been used for the past few years to improve nanoparticle. The combination of high molecular materials and nanoparticles can improve the defects, significantly. However, the disadvantages of low stability in blood and normal tissues accumulation still cannot be overcame, and they also influence the application of the nanoparticle release system in the field of biomedicine.
Nanoparticles are self-assembled vesicles having a spherical bilayer structure surrounding an aqueous core domain. Due to their intrinsic biocompatibility and ease of preparation, several nanoparticle drug systems have been approved. In addition, modified nanoparticles have been shown to have excellent pharmacokinetics profiles for the delivery of nucleic acids, proteins, and chemotherapeutic agents such as doxorubicin. However, major drawbacks of nanoparticle-based drug carriers include their instability and the lack of tunable triggers for drug release. As such, there have been several attempts at enhancing the properties of nanoparticles. For example, incorporation of polymerizable lipid amphiphiles leads to crosslinked nanoparticles with higher stability. Unfortunately, every nanoparticle would require a specific polymerizable amphiphile, making this approach synthetically cumbersome.
In addition, the crosslinks and modification of high molecule often allow for controllable release of the payload. To provide a combination of stability and modification generality, hydrophilic polymers such as poly(ethylene glycol) (PEG) have been added to liposomes. However, these modifiers can easily dissociate from the liposome surface, returning them to the unstable state. In addition, nanoparticle formed by covalent linkage of polymer still have the disadvantages of protein absorption, low drug release and large accumulation in normal tissues. Thus, there are a lot of adverse effects resulting from the use of nanoparticle. For example, (1) the active substance cannot be delivered to and released in the target site since nanoparticle is absorbed with protein resulting in the unstable of nanoparticle; (2) the active substance is largely accumulated in normal tissues that result in metabolism problems.
Accordingly, a novel nanoparticle is required to avoid protein absorption, low drug release rate, and the large accumulation in normal tissues. The nanoparticle with high stability and high release rate can deliver the drug to target cell and avoid protein absorption. Therefore, the amount of drug and side-effect caused by drugs can be decreased to reduce the risk of death attributed to the side-effect of medicine.